In recent years, a major technical challenge to the petroleum refining industry has been the need to establish new means for producing high octane gasolines containing oxygenates in response to pollution control regulations requiring the elimination of lead from gasoline, which was previously employed as an octane enhancer. Further, the development of more efficient, higher compression ratio gasoline engines which require higher octane fuels have spurred the industry to produce new octane enhancers.
Initially, to meet these requirements, the industry developed non-lead octane boosters and reformulated high octane gasoline to incorporate increased fractions of aromatics and branched hydrocarbons. While these and other approaches were sufficient to meet the technical requirements of regulations requiring the elimination of lead, the economic impact on the cost of gasoline was significant.
Accordingly, the industry has intensified their effort to discover new processes to manufacture the gasoline products required by the marketplace. In particular, the industry has centered on blending gasoline with lower aliphatic alkyl ethers as octane enhancers. To this end, methyl tertiary butyl ether (MTBE) has been found especially useful as an octane enhancing additive. Therefore, improvements to the processes relating to the production of MTBE have become increasingly important in the petrochemical industry.
It is known that isobutylene may be reacted with methanol over an acidic catalyst to produce MTBE. Methanol is generally in ample supply, but the supply of isobutylene is limited since it is formed only in cracking operations, primarily catalytic cracking and olefins production. Since insufficient isobutylene is available from these sources to meet the growing industry needs, many C.sub.4 production facilities based on dehydrogenation of isobutane are being used to prepare isobutylene feedstocks for MTBE production. See, e.g., Al-Muddarris, U.S. Pat. No. 4,329,516. However, such facilities have proven very expensive to build and operate.
It would therefore represent a notable advancement in the state of the art if a process which provided for the increased production of MTBE from available feedstocks could be developed. To this end, the present inventors have developed an integrated process for the production of MTBE from readily available mixed C.sub.4 feedstocks.